Performance Recorded on Paper
Page 35
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T0 be shown for the first time at the Engineering and Marine Exhibition, at Olympia, London, from August 28September 13, the Dobbie McInnes recording accelerometer produces a permanent record of vehicle performance.
In principle, the instrument embodies a spring-driven drum, over which a roll of graph paper is carried. An inkoperated pen, which is linked to weights and dampers, records by a line on the graph paper any movement made by the weights.
By this means a record of acceleration may be produced to correspond in feet per sec. per sec.; lb. per ton; or per cent of "g" on an accurate time basis. It will show at the same time pauses for gear changing, tractive resistance and smoothness of clutch.
A true braking curve can be obtained. as the machine is not sensitive to the tilt of the vehicle on its springs, The brake curve will record an analysis of events between the initial action of braking to standstill, giving the true brake efficiency.
Gradients may be recorded, provided that a steady speed is maintained and the machine is set at zero on a level road. Tractive effort on hills can be recorded in the same manner.
A further use for the recorder is found by mounting it on any part of a vehicle to determine the suspension and damping qualities of the chassis: Frequencies in any direction can he measured up to 20 per sec., the vertical readings being those which will normally affect comfort, whilst the transverse readings will give the cornering and side sway accelerations, all of which can be interpreted as forces.
The apparatus is made by Dobbie McInnes, Ltd., 57, Bothwell Street, Glasgow, C.2.